C program structure
Before we learn the basic
building blocks of the C language, let's take a look at a minimal C program
structure, which can be used as a reference in the following sections.
C Hello World instance
The C program mainly
consists of the following:
·
Preprocessor directive
·
function
·
variable
·
Statement &
expression
·
Annotations
Let's look at a simple
code that can output the word "Hello World":
Examples
#include < stdio.h >
Int main ( )
{
/ * my first C program * /
printf( " Hello, World! \ N " ) ;
return 0 ;
}
Next we explain the above
procedure:
1. The first line of the program #include
<stdio.h> is a preprocessor directive that tells the C compiler
to include the stdio.h file before actually compiling.
2. The next line int main () is
the main function, the program from here to start.
3. The next line /*...*/ will be ignored by the
compiler, where the contents of the program will be placed. They are
called annotations of the program.
4. The next line, printf (...), is
another function that is available in C and displays the message "Hello,
World!" On the screen.
5. The next line returns 0; terminates
the main () function and returns the value 0.
Compile & execute C program
Let's take a look at how
to save the source code in a file and how to compile it and run it. Here
are the simple steps:
1. Open a text editor and add the above code.
2. Save the file as hello.c .
3. Open the command prompt and go to the
directory where the saved file is located.
4. Type gcc hello.c , enter the
carriage return, compile the code.
5. If there is no error in the code, the command
prompt jumps to the next line and generates the a.out executable.
6. Now, type a.out to execute
the program.
7. You can see "Hello World" on
the screen .
$ Gcc hello.c
$ ./a.out
Hello, World!
Make sure that your path
already contains the gcc compiler and that you are running it in the directory
containing the source file hello.c.
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